Known air springs consist generally of a diaphragm made of rubberized textile material which is capable of deformation, and of a metal armature, a closing element connecting thereto and providing airtight closure. The function of the closing element is to affix the air spring to the suspended body (e.g. a vehicle) and also to assure inlet and outlet of the actuating air. Airtight closure is to be established between the flanges of the diaphragm and the closing element so, as to be able to maintain increased pressure caused by springing in the full length of the spring path, i.e. to achieve airtight closure even upon the effect of tensile forces upon the extreme release of springs.
Several solutions have been proposed for the structure of the system consisting of the closing element and the diaphragm. FIGS. 1-5 show various air spring structures employed in the prior art.
With one type of known air spring the flanges of the diaphragm are fixed between the two metal parts by the compressive force of screws. Such a solution is shown in FIGS. 1 and 2, wherein compressive force provides a hermetic sealing and keeps the flange of the diaphragm in the proper position.
FIG. 1 shows in a partially sectional view, the clamping flange of the diaphragm on an air spring and the manner of assembly for achieving hermetic sealing.
With the solution known from practical manufacturing throughout the world, the flange of a diaphragm 1 is fitted into an appropriately shaped part of a closing element 2. This operation is rather difficult due to a vulcanized marginal wire 5. Then a fixing lid 3 if fitted onto usually at least eight circumferential screws contained in the closing element 2. The closing lid also contains the connection for air, and it is fixed to the closing element 2 by nuts 4. The structure is sealed after having tightened the nuts with the proper torque.
FIG. 2 is a partial sectional view of a well known solution. Here the hermetic closure is also obtained by means of screws. In comparison to the structure of FIG. 1 the essential difference is that the diaphragm flange 6 is turned by 180.degree. in relation to the flange of the diaphragm 1. Considering that the flange 6 is fitted to a closing element 7 along a shorter periphery than the diaphragm 1 of FIG. 1, there are usually fewer, such as from 1 to 4 fixing screws 8 of the closing element 7, and the tolerances of the production are not so tight. Arrangement of the fixing lid 9 and air-connection 10 corresponds to the similar element in FIG. 1. The drawback of clamping -- as to be seen in FIGS. 1 and 2-- is the high cost and the complicated nature of the mounting.
FIG. 3 shows in partial section the flange part of a conventional air spring. In this case formation of the rolling diaphragm 11 corresponds to that of FIG. 1, except that here the lid is not installed by screws, but it is a compressed, flanged lid 12. That means that the diaphragm cannot be disassembled when it becomes damaged, and the lid 12 must be discarded together with the air connection 13 thereon and all the other fittings and connections.
FIG. 4 illustrates in partial cross section a formation of the customary flange, showing the entire air spring and the hermetic flange mounting. The flange of the diaphragm 14 is pulled onto the profiled ring 16 which is welded onto the fixing lid 15. In this case airtight sealing is obtained by dimensional overlapping, while resistance to downwards motion of the flange of the diaphragm can be achieved only by the adhesion of the overlapping, close fitting of the conical surfaces. This solution can be easily assembled, however, in an extreme springing position the diaphragm may slide down easily from the profiled ring 16.
FIG. 5 is a partial cross-sectional view of a known air spring, illustrating a frequently used method for fitting the flanges and metal parts. In this case, as mentioned in connection with FIG. 4, an air-tight closure is obtained on the conical surfaces of the metal and the flange of the diaphragm, establishing a proper overlap. The extent of overlap and the cone angle influence the quality of the assembly, airtightness and pulling force, i.e. the force, which is needed for removing the diaphragm from the metal part. To obtain proper overlap and fit, most accurate assembly is necessary. However, problems may arise even with the highest accuracy, in connection with the resistance to pulling forces. These are structures in which a nose-part is formed on the conical surface to provide resistance to sliding down, are aimed at the solution of that problem.
It is clear from FIG. 5 that the locking ring 17 is provided with the nose-part 17a backsliding of the diaphragm 18. Accordingly, sliding up of the flanges of the diaphragm 18 requires a far higher inner overpressure, than e.g. positioning of a marginal ring. Prevention of backsliding of the diaphragm 18 is of utmost importance also with diaphragms operated at low pressure. The advantage of the nose-part 17a lies in that is prevents backsliding of the diaphragm in air springs operated in extreme positions, such as in the case of complete release of the spring.
It is a disadvantage that the nose-part 17a requires most accurate assembly, because it can be formed only with expensive cutting. Also mounting requires special tools and high internal pressure.
The mode of fixation i.e. combined application of flange-formation and of the ring with the nose-like cross-section, represents the prior art, as it is described DE-AS 3,246,599.
Further modes of fixation result in unreleasable bonds between diaphragm, closing element and sometimes the piston (see e.g. German Federal Republic allowed application No. 3,246,962). Therefore, when the rubber becomes damaged, the entire structure has to be thrown away and this is both uneconomical and inimical to the environment.